One method of manufacture of top-of-the-line lipsticks involves making the lipstick container in two connected parts: an ornamented base and a tubular cartridge assembly held together by a barb- or latch-type joint. This is a more secure method than the more conventional systems, such as press fits or hot-melt adhesive. In addition, the barb-type joint is well suited to the realities of economy and logistics: it is sometimes desirable to ship the lipstick to another location from the manufacturer so that it can there be filled with the molded pomade. After filling, the cartridge can be sent back to the manufacturer. In making the lipstick container in two parts, base and cartridge, the cartridge can be shipped to the filler separately without the base, thus saving shipping costs and container space. The final snap assembly of the base and cartridge can be done when the unit is received back at the manufacturer after filling. The cover is also applied.
It has been the experience in the industry that these expensive lipsticks have occasionally, when dropped, failed at the barb-type fastener on impact so that the cartridge comes loose and slams against the top of the cover and the pomade breaks free from its cup and is damaged beyond use. As a precaution against such failure, the industry now demands a testing program for such lipstick containers. This test involves the intentional dropping of the lipsticks with cover on and pomade down from a height of several feet onto a solid surface. Such testing is now routine.
To satisfy the customer and, incidentally, to pass this stringent test, the Applicant has investigated the cause of such failure in the past. After this careful investigation it has been confirmed that the separation of the cartridge and the base has invariably been caused by the failure of the barb latches which hold the two parts together. Often these latches are in the form of a pair of cantilevered hooked spring latches formed unitarily with the molded plastic base. The hooks, facing outward, engage in assembly over the top of an annular upward shoulder in the lipstick innerbody or "inner".
In the impact of the drop test, the downwardly falling lipstick experiences an immediate stop as it lands. The cartridge with its pomade, having some mass, and having built up velocity in the fall, wants to continue the travel. The result is that there is stress on the snap fastener structure which induces disengagement.
The purpose of the present invention, therefore, is to present means for assuring that the latches described above do not disengage from the inner in such a fall.